Spin-Orbit Torque in Bilayers of Kagome Ferromagnet Fe3Sn2 and Pt

Spin-orbit torque manipulation of sub-terahertz magnons in antiferromagnetic α-Fe2O3

The ability to electrically manipulate antiferromagnetic magnons, essential for extending the operating speed of spintronic devices into the terahertz regime, remains a major challenge. This is because antiferromagnetic magnetism is challenging to perturb using traditional methods such as magnetic fields. Recent developments in spin-orbit torques have opened a possibility of accessing antiferromagnetic magnetic order parameters and controlling terahertz magnons, which has not been experimentally realised yet. Here, we demonstrate the electrical manipulation of sub-terahertz magnons in the α-Fe2O3/Pt antiferromagnetic heterostructure. By applying the spin-orbit torques in the heterostructure, we can modify the magnon dispersion and decrease the magnon frequency in α-Fe2O3, as detected by time-resolved magneto-optical techniques. We have found that optimal tuning occurs when the Néel vector is perpendicular to the injected spin polarisation. Our results represent a significant step towards the development of electrically tunable terahertz spintronic devices.

Magnetodynamic properties of ultrathin films of Fe[Formula: see text]Sn[Formula: see text]-a topological kagome ferromagnet

Fe[Formula: see text]Sn[Formula: see text] is a topological kagome ferromagnet that possesses numerous Weyl points close to the Fermi energy, which can manifest various unique transport phenomena such as chiral anomaly, anomalous Hall effect, and giant magnetoresistance. However, the magnetodynamic properties of Fe[Formula: see text]Sn[Formula: see text] have not yet been explored. Here, we report, for the first time, the measurements of the intrinsic Gilbert damping constant ([Formula: see text]), and the effective spin mixing conductance (g[Formula: see text]) of Pt/Fe[Formula: see text]Sn[Formula: see text] bilayers for Fe[Formula: see text]Sn[Formula: see text] thicknesses down to 2 nm, for which [Formula: see text] is [Formula: see text], and g[Formula: see text] is [Formula: see text]. The films have a high saturation magnetization, [Formula: see text], and large anomalous Hall coefficient, [Formula: see text]. The large values of g[Formula: see text], together with the topological properties of Fe[Formula: see text]Sn[Formula: see text], make Fe[Formula: see text]Sn[Formula: see text]/Pt bilayers useful heterostructures for the study of topological spintronic devices.

Uncovering the Kagome Ferromagnet within a Family of Metal-Organic Frameworks

Kagome networks of ferromagnetically or antiferromagnetically coupled magnetic moments represent important models in the pursuit of a diverse array of novel quantum and topological states of matter. Here, we explore a family of Cu²⁺-containing metal-organic frameworks (MOFs) bearing kagome layers pillared by ditopic organic linkers with the general formula Cu₃(CO₃)₂(x)₃·2ClO₄ (MOF-x), where x is 1,2-bis(4-pyridyl)ethane (bpe), 1,2-bis(4-pyridyl)ethylene (bpy), or 4,4'-azopyridine (azpy). Despite more than a decade of investigation, the nature of the magnetic exchange interactions in these materials remained unclear, meaning that whether the underlying magnetic model is that of an kagome ferromagnet or antiferromagnet is unknown. Using single-crystal X-ray diffraction, we have developed a chemically intuitive crystal structure for this family of materials. Then, through a combination of magnetic susceptibility, powder neutron diffraction, and muon-spin spectroscopy measurements, we show that the magnetic ground state of this family consists of ferromagnetic kagome layers that are coupled antiferromagnetically via their extended organic pillaring linkers.

Intrinsic anomalous Hall effect in thin films of topological kagome ferromagnet Fe3Sn2

Fe₃Sn₂, a kagome ferromagnet, is a potential quantum material with intriguing topological features. Despite substantial experimental work on the bulk single crystals, the thin film growth of Fe₃Sn₂ remains relatively unexplored. Here, we investigate the effect of two different seed layers (Ta and Pt) on the growth of Fe₃Sn₂ thin films. We demonstrate the growth of polycrystalline Fe₃Sn₂ thin films on Si/SiO₂ substrates by room temperature sputter deposition, followed by in situ annealing at 500 °C. Our structural and magnetic measurements indicate that a pure ferromagnetic phase is formed for the Pt/Fe₃Sn₂ thin films with higher saturation magnetization of M_s = 464 emu cc^-1, while a mixed-phase (consisting of ferromagnetic, Fe₃Sn₂ and antiferromagnetic, FeSn) is formed for the Ta/Fe₃Sn₂ thin films with a lower M_s of 240 emu cc^-1. The Pt/Fe₃Sn₂ thin films also exhibit an anomalous Hall coefficient, R_s ≈ 2.6 × 10^-10 Ω cm^-1 G^-1 at room temperature, which is two order of magnitude higher compared to 3d-transition metal ferromagnets. A non-zero temperature-independent anomalous Hall conductivity σintxy = (23 ± 11) Ω^-1 cm^-1 indicates an intrinsic mechanism of anomalous Hall effect originating from Berry curvature. These results are important for realizing novel topological spintronic devices on a CMOS-compatible substrate.